Yemen’s southern separatists withdrew on Saturday from some governmental buildings they had seized in Aden last week, but they kept camps giving them control of the southern port of Yemen, where the Saudi-backed government is located.

Last week, the southern separatists backed by the UAE took over Aden stirring tension within the Saudi-led military alliance to counter the Iranian-backed Houthi movement. The move could also stir old conflicts between the two Yemeni parts that were united in 1990 in a one state.

The Saudi-led coalition in Yemen launched air strikes and dropped light bombs on the Aden at dawn on Saturday near camps for southern separatist fighters after the alliance renewed its call for them to withdraw from all positions they occupied last week.

The coalition called on all forces in the south to unite under the umbrella of the coalition to fight the Houthis.

In response to the Saudi light bombs, a brigade fighting with southern separatists said that “their forces will not back down, and the Saudi aircrafts will not scare them [the separatists].”

Conflict in Yemen has erupted in September 2014, when the Ansar Allah group “Houthi” backed by Iran, seized control of the Yemeni capital Sanaa. Following the Houthi action Saudi Arabia, the closest regional power to Yemen announced in March 2015, forming the Coalition for Supporting Legitimacy in Yemen.

Meanwhile, Saudi Arabia said that the Houthis attacked on Saturday the “Shaybah” oil field in the eastern part of the kingdom close to its borders with the UAE. Riyadh said that three drones were used in the attack

A military spokesman for the Houthi movement said the movement had launched 10 drone attacks on oil facilities in the Shaybah field in eastern Saudi Arabia, describing the attacks as the biggest offensive in Saudi depth. He vowed more operations against the kingdom.

In a televised speech, Abdul-Malik Al-Houthi, leader of the Houthi movement, said that the recent actions in Aden “proved the coalition is in crisis and [the Yemeni president Abdrabbuh Mansour] Hadi had no authority.”

Additionally, the Houthi movement appointed an ambassador to Iran in a move was rejected by the Yemeni legitimate government.

The conflict in Yemen resulted in killing more than 100,000 civilians and wounding another hundreds of thousands. It also a humanitarian crisis in the poor country as well as medical issues. Yemen is facing the world’s largest humanitarian crisis.